Solid-state ignition system for outboard motors

ABSTRACT

An outboard motor includes a cowl and frame vibrationally isolated from the engine. A capacitor discharge ignition circuit includes a capacitor connected to a battery through a charging circuit and to the distributor and thereby the spark plugs through a silicon controlled rectifier and pulse transformer. The system components are housed within a metal box which is secured and grounded to the cowl frame. The common or ground side of a battery is directly connected to the grounded cowl frame and the positive side is connected directly to the charging circuit and to the starter. A relatively substantial jumper lead interconnects the cowl frame to the engine block. The transformer is suitably mounted within the outboard motor and connected to the ignition system by suitable leads and to the spark plugs through the usual distributor. In operation, any high voltage transients developed between the cowl frame and the engine block are not impressed across the ignition system.

United States Patent [72] inventor Floyd M. Minks Campbellsport, Wis. [21] Appl. No. 731,689 [22] Filed May 30, 1968 [45] Patented Jan. 19, 1971 [73] Assignee Brunswick Corporation Chicago, Ill. a corporation of Delaware Continuation of application Ser. No. 539,532, Apr. 1, 1966, now abandoned.

[54] SOLID-STATE IGNITION SYSTEM FOR 146.5A. 148DC, 148E; 290/179 388; 315/2091,

[56] References Cited UNITED STATES PATENTS 3,035,108 5/1962 Kaehni 123/148 OTHER REFERENCES Popular Electronics of 6- 63 (pages. 33- 38 & 86) copy 315- 209T Radio & Television News of 7- 55 (pages 62, 63, 90, 91) copy l23- 148E consumer Electronics of 10- 64 (6 pages) copy 3l5 209T Ford Truck Shop Manual of 1957 (pages 1 40, l 41, l 63, 8 24, 8- 25, copy in Gr. 342.

Primary Examiner-Laurence M. Goodridge Att0rney-Andrus, Sceales, Starke & Sawall ABSTRACT: An outboard motor includes a cowl and frame vibrationally isolated from the engine. A capacitor discharge ignition circuit includes a capacitor connected to a battery through a charging circuit and to the distributor and thereby the spark plugs through a silicon controlled rectifier and pulse transformer. The system components are housed within a metal box which is secured and grounded to the cowl frame. The common or ground side of a battery is directly connected to the grounded cowl frame and the positive side is connected directly to the charging circuit and to the starter. A relatively substantial jumper lead interconnects the cowl frame to the engine block. The transformer is suitably mounted within the outboard motor and connected to the ignition system by suitable leads and to the spark plugs through the usual distributor.

In operation, any high voltage transients developed between the cowl frame and the engine block are not impressed across the ignition system.

ENGINE BLOCK SOLID-STATE IGNITION SYSTEM FOR OUTBOARD MOTORS Thisapplication is. a continuation. of application Ser. No. 539,532 filed Apr. I, I966; now abandoned.

This invention relates to a solid-state ignition system for in- .ternal combustion engines and particularly-to the mounting and connection of engine. ignition systemsinto the engine firing circuit for outboard motors and the like.

Ignition systems of a solid-state or'transistorized variety have'been suggested for internal-combustion engines. Such units minimize certain problems associated with conventional ignition systems. A highly satisfactory ignition system for internal-combustion engines and particularly outboard motors is shown in applicants copending application entitled Solidstate Ignition System .which .is being filed on even date herewith and is assigned. to the same assignee as the present application. As more fully disclosed therein, a capacitor is periodically charged through a triggered oscillator and discharged through the firing of a silicon controlled rectifier and pulse transformer. As disclosed in that application, the ignition system is constructed as a potted unit within a suitable metal box with the heat sensitive element secured to the base of the box. The ignition housing or box is'directly mounted to a cowl frame in the path of the air passed to the carburetor means. to provide. maximum dissipation of the heating and to isolate the ignition system from the engine vibrations.

Inv the development of a solid-state ignition system, failure of the solid-state components was encountered without any apparent reason. I

As disclosed in the previously identified copending application, the cowl and its frameare vibrationally isolated from the engine. 'A jumper lead was normally eonnected therebetween damaging voltage transients between the engine block and cowl. Although this transient is of extremely short duration of the order of IO nanoseconds. (l' ,sec'.), applicant realized the magnitude of the order of several thousand voltswas such that applied directly across the ignition systemwould damage the units and further that thev distributed'impedances could not be practically reduced to a degree toprevent such damaging voltages.

The, present invention is particularly directed to an improved circuit connection positively preventing application of the high voltage transients across the ignition'syste'ms. In ac- .cordance with the, present invention, the common or ground ,to pre ent creation of high voltagestherebetween. The igniside of'the battery is directly connected to the grounded cowl 1 unit. A relatively substantial jumperl'ead interconnects the cowl .unit to the engine blockto form thefcommon intercon- -nection between the ignition system and the engine blockas this jumperlead must carry starter current when employing an electric start. The coil is suitably mounte'dwithin the outboard motor and connected to the ignitionfsystem by suitable leads andto the spark plugs through the usual distributor.

In operation, any high voltage transients developed between the cowl unit and the engine bIock-areYnot impressed across the ignition system. Consequently, failure of components from the voltage transients has been essentially eliminated.

The'present invention thusprovidesa simple and inexpensive. means for maintaining the operation. of the ignition system in an internal combustion engine. The drawing furnished herewith illustrates a preferred construction of the present invention in which the above advantages and features are. clearly.shown as well as others which will be clear from the following description.

In the drawing:

FIG. I is a partial sectional view. of an outboard motor with a solid-state ignition system'mounted and connected in accordance with the present invention; and

FIG. 2 is a diagrammaticillustration. of the outboard motor and the connection of the ignitionsystem'into the circuit in accordance with the present invention.

Referring to the drawing and particularly to FIG. I, an out- .board motor I for driving a watercrafnnot shown, is shown is attached to and vibrationally isolated from theengine 2 and the drive shaft housing 3.

Asolid-state ignition unit6 is mounted directly to the cowl frame assemblyS. A battery 7provides an initial source of energy, and is connected to the ignition unit6 and an electric starter 8 through a plug connector 9.

The ignition unit 6 is connected through a transformer 10 for firing of the spark plugs ll...The transformer 10 is mounted within the cowl assembly and connected by a lead 12 to a distributor, not shown, in-FlG. l. The-distributor sequentially connects the transformer-I0 to, theseveral spark plugs 11 for proper sequential firing of the spark plu'gsand operation of the engine. l

The batteryconnection includes the plug type connector 9 for releasably interconnecting of the engine circuit to the battery 7 and a remote electricalcontrollli. The connector 9in- .cludes an external hamess'l l connected to the battery 7 and the control 13 and an engine harness 15 secured to the lower cowl member I6. The several leads from the engine harness vl5 are described insufficient detail to'clearly describe the into provide the ground connectionlA'third. lead 20 is connected through the connector 9 to the positive or high voltage battery] terminal to the starter 8. through a starter solenoid 21. A ground jumper lead 22 interconnects the cowl frame member 5 to the engine block 2 and; establishes the ground connection from the starter to the cow! frame.

Referring particularly to FIG. 2, an'ignition system is schematically and briefly shown includinga capacitor "23 connected to the battery 7 through a'DCtoDC converter 24 which includes a capacitor charging circuit, now shown. The capacitor 23 is connectedin a discharge circuit including the transformer 10 and a silicon controlled re'ctifier 25. A set of points 26v such as conventional points areshown and-are connected in the circuit in any suitable manner to periodically fire the siliconv controlled rectifier 25 for discharging of the capacitor 23 into the coil unit 10 and through a distributor 26 into a spark plug II. For a more detailed description of the ignition system reference may be made to applicant's previously identified application. 1

In FIG. 2, the 'cowlihg and the engine block are diagrammatically shown. Additionally, the jumper lead22 is shown with, a series connected inductanceelement 27 which indicates the inherent inductance of the lead as such and not a separate element connected in the circuit. The inductance of the coil and distributor leads, the diltributed capacitance of which, when the gap fires, can cause high transient voltages to exist between the cowlingand the engine block for short periods, in the order of nanoseconds, but of sufficient magnitude to damage solid-state components.

Prior to firing of the gap, capacitor 29 is charged. When the gap 11 fires, the series circuit is completed and the voltage across the capacitor 29 is divided between inductances 27 and 28. Generally the inductances are of a similar size and the voltage divides more or less equally; The voltage of capacitor 29 will be of the order required to break down the gap 11 and may easily be of the order of 10,000 volts. with a resulting 5,000 volts appearing across the inductance 27 and therefore between the cowl 5 and the engine 2. Such voltages appearing for the order of nanoseconds are not generally of any serious consequence. However, applicant has realized and discovered that the voltages did damage and in fact often destroyed solid state electronic components.

In accordance with the teaching of this application, the ignition unit is connected directly between the positive and the negative leads of the battery 7 through the common or ground connection to the cowl frame, rather than the usual connection of the battery negative directly to the engine block. This eliminates the supposition of high voltage transients on the battery voltage as applied to the input of the ignition unit 6. Thus, a reliable and improved circuit operation is provided. Thus, applicant has perceived a severe limitation in the normal connection of the battery ground lead directly to the engine and avoided the attendant problem in an exceptionally simple and inexpensive manner.

lclaim:

1. In an outboard motor having an internal combustion engine unit with the engine connected to and electrically insulated from a support including a cowl-supporting frame supported upon electrically insulating members providing substantial electrical impedance at high frequency therebetween, the improvement in the electrical system for the engine comprising an electrical ignition operating unit including an ignition system having solid-state components, means mounting said ignition system on said frame and being grounded to the frame, a battery for said engine including a first lead connected to the ignition system and a second lead directly connected to the frame, a direct current starter for said engine mounted upon the engine and including a first terminal connected through a normally open switch means to the ungrounded terminal of said battery and grounded to the engine. and a ground lead connected between the engine and the frame whereby high voltage transients appearing between the engine and the support do not appear superimposed on the power supply voltage connected across said solid-state components.

2. The outboard motor unit of claim 1 wherein said ignition system is housed within a metallic housing and having means mounting the housing directly on the frame to establish the ground connection therebetween.

3. The outboard motor unit of claim 2 wherein said ignition system is a capacitor discharge system including a discharge capacitor and a transistorized converter for charging the capacitor, said ignition system being housed within a metallic housing having said converter grounded to the housing and having means mounting the housing directly on the frame to establish the ground connection therebetween.

4. The outboard motor unit of claim 2 wherein said isolating members are rubberlike mounts to vibrationally isolate the cowl frame from the engine and said ignition system being housing within a metallic housing and having means mounting the housing directly on the frame to establish the ground connection therebetween.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No- 3,556,069 Dated January 19, 1971 Inventoflx) FLOYD M. MINKS It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 2, Line 14, cancel "now" and substitute not Column 2, Line 53, cancel "now" and substitute not Column 2, Line 56, cancel "26" and substitute not shown, and in the same line, cancel "are shown" Column 2, Line 69, after "and" (first occurrence) insert the distributed capacitance Column 2, Line 70, after "distributor" insert spark Column 3, Lir 23, cancel "supposition" and substitute therefor superimposing and at Column 4, Line 31 (Claim 4) cancel "housing" (first occurrence) and substitute housed Signed and sealed this 6th day of Jul 1971 (SEAL) Attest:

WILLIAM E. SCHUYLER, Commissioner of Paton EDWARD M FLETGHERJR. Attesting Officer 

1. In an outboard motor having an internal combustion engine unit with The engine connected to and electrically insulated from a support including a cowl-supporting frame supported upon electrically insulating members providing substantial electrical impedance at high frequency therebetween, the improvement in the electrical system for the engine comprising an electrical ignition operating unit including an ignition system having solid-state components, means mounting said ignition system on said frame and being grounded to the frame, a battery for said engine including a first lead connected to the ignition system and a second lead directly connected to the frame, a direct current starter for said engine mounted upon the engine and including a first terminal connected through a normally open switch means to the ungrounded terminal of said battery and grounded to the engine, and a ground lead connected between the engine and the frame whereby high voltage transients appearing between the engine and the support do not appear superimposed on the power supply voltage connected across said solid-state components.
 2. The outboard motor unit of claim 1 wherein said ignition system is housed within a metallic housing and having means mounting the housing directly on the frame to establish the ground connection therebetween.
 3. The outboard motor unit of claim 2 wherein said ignition system is a capacitor discharge system including a discharge capacitor and a transistorized converter for charging the capacitor, said ignition system being housed within a metallic housing having said converter grounded to the housing and having means mounting the housing directly on the frame to establish the ground connection therebetween.
 4. The outboard motor unit of claim 2 wherein said isolating members are rubberlike mounts to vibrationally isolate the cowl frame from the engine and said ignition system being housing within a metallic housing and having means mounting the housing directly on the frame to establish the ground connection therebetween. 